DADD-
Looks like your wife was right (again) ....despite her warning you F'd
up again.
Now you have a nice groove to act as a real crud catcher and you've
given her maint problem.
Often times stone tiles are set with epoxy grout...my experience,
epoxy grout is a better adhesive but is softer.
Stop messing with it.

A simple test is to put some of the crud in her mouth. If it is
grout, it will have no taste... If it is crud, it will make her throw
up.... By observing the effect, you will either win or lose the
argument....

It's crud to me. Any recessed gap like those on a countertop are
bound to collect crud. My bathroom floor tiles are much better
grouted and easier to sanitize than that countertop.
If it wasn't crud it wouldn't scrape put with a screwdriver. And if
it's soft grout, it's still crud. Countertop grout should be hard,
otherwise you might as well call it caulk. It's probably a poorly
mixed grout in there.
Clean it out and re-grout using a properly hard-setting grout, flush
or almost flush with the top.
I'm not even thinking about food safety, which is a real issue.
Just the thought of food being prepped around crud is unappetizing.
Your choice is epoxy or cement based, colored black. I'd probably use
cement, and if didn't work out after some years, I'd grind out the top
3/16" or so and try epoxy. That's not a big job on your countertop.

Log in

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.